Carbenoid insertion into zirconacycles
Carbenoid insertion into zirconacycles
Insertion of E-1,2-dihalo-1-lithioethene into zirconacyclopentenes formed methylenecyclopentenes. The mechanism proposed involves initial formation of an alkyne that then inserts intramolecularly into a carbon-zirconocenium bond. Stable alcohol products have been formed from hydroboration of the exocyclic double bond followed by basic peroxide quench. The same methylenecyclopentenes were formed from insertion of 1-lithio-2-haloethynes via a novel zirconocene vinylidene. Insertion of the carbenoid into a zirconacyclopentane formed an alkyne, but also showed for the first time that a neutral zirconium species will rearrange to incorporate a carbenoid fragment at room temperature, in this case forming a bis-insertion product.
Intramolecular carbenoid insertion was attempted, but the area of research failed to give positive results. Some substrates with carbon-chlorine bonds were found to be incompatible with the zirconium cyclisation method.
The range of vinyl carbenoids inserted into zirconacyclopentanes and - enes has been extended. Novel polyinsertion of vinyl carbenoids into the same side of zirconacyclopentanes has been discovered, revealing the fluxionality of the intermediate zirconate species. A novel rearrangement of zirconacyclohexane to form phenyl substituted methylenecyclopentenes has also been discovered.
The first insertion of carbon monoxide into a zirconacyclohexane to form a cyclohexanone is reported. The insertion of phenylsulfone or vinyl carbenoids followed by butyl isocyanide has been found to form functionalised cyclohexanones after acidic quench. The ‘one pot’ formation of a bicyclic cycloheptanone from an acyclic precursor, with five new regioselectively formed carbon-carbon bonds, was discovered; thus revealing the degree of elaboration possible with organozirconium chemistry.
University of Southampton
Norton, David
4c63fcf9-0fc8-4623-b414-443d4658bbed
2004
Norton, David
4c63fcf9-0fc8-4623-b414-443d4658bbed
Norton, David
(2004)
Carbenoid insertion into zirconacycles.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Insertion of E-1,2-dihalo-1-lithioethene into zirconacyclopentenes formed methylenecyclopentenes. The mechanism proposed involves initial formation of an alkyne that then inserts intramolecularly into a carbon-zirconocenium bond. Stable alcohol products have been formed from hydroboration of the exocyclic double bond followed by basic peroxide quench. The same methylenecyclopentenes were formed from insertion of 1-lithio-2-haloethynes via a novel zirconocene vinylidene. Insertion of the carbenoid into a zirconacyclopentane formed an alkyne, but also showed for the first time that a neutral zirconium species will rearrange to incorporate a carbenoid fragment at room temperature, in this case forming a bis-insertion product.
Intramolecular carbenoid insertion was attempted, but the area of research failed to give positive results. Some substrates with carbon-chlorine bonds were found to be incompatible with the zirconium cyclisation method.
The range of vinyl carbenoids inserted into zirconacyclopentanes and - enes has been extended. Novel polyinsertion of vinyl carbenoids into the same side of zirconacyclopentanes has been discovered, revealing the fluxionality of the intermediate zirconate species. A novel rearrangement of zirconacyclohexane to form phenyl substituted methylenecyclopentenes has also been discovered.
The first insertion of carbon monoxide into a zirconacyclohexane to form a cyclohexanone is reported. The insertion of phenylsulfone or vinyl carbenoids followed by butyl isocyanide has been found to form functionalised cyclohexanones after acidic quench. The ‘one pot’ formation of a bicyclic cycloheptanone from an acyclic precursor, with five new regioselectively formed carbon-carbon bonds, was discovered; thus revealing the degree of elaboration possible with organozirconium chemistry.
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Published date: 2004
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Local EPrints ID: 465309
URI: http://eprints.soton.ac.uk/id/eprint/465309
PURE UUID: 7c03b069-7e8c-4834-884e-97edd6ca2902
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Date deposited: 05 Jul 2022 00:37
Last modified: 16 Mar 2024 20:06
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Author:
David Norton
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